Conventionally, in the manufacture of semiconductor devices, micro-processing by lithography using a photoresist composition has been carried out. The micro-processing is a processing method comprising forming a thin film of a photoresist on a silicon wafer, irradiating actinic rays such as ultraviolet rays through a mask pattern on which a pattern for a semiconductor device is depicted, developing it to obtain a photoresist pattern, and etching the substrate using the photoresist pattern as a protective film. However, in recent progress in high integration of semiconductor devices, there has been a tendency that shorter wavelength actinic rays are being used, i.e., ArF excimer laser beam (wavelength 193 nm) has been taking the place of i-line (wavelength 365 nm) or KrF excimer laser beam (wavelength 248 nm). Along with this change, influences of random reflection and standing wave of actinic rays from a substrate have become serious problems. Accordingly, it has been widely studied to provide an anti-reflective coating between the photoresist and the substrate (bottom anti-reflective coating). In addition, micro-processing by lithography using F2 excimer laser beam (wavelength 157 nm) that is a light source having a shorter wavelength has been considered.
As the anti-reflective coatings, inorganic anti-reflective coatings made of titanium, titanium dioxide, titanium nitride, chromium oxide, carbon or α-silicon, etc. and organic anti-reflective coatings made of a light-absorbing substance and a high molecular weight compound are known. The former requires an installation such as a vacuum deposition apparatus, a CVD apparatus or a sputtering apparatus, etc. In contrast, the latter is considered advantageous in that it requires no special installation so that many studies have been made. For example, mention may be made of the acrylic resin type anti-reflective coating having a hydroxyl group being a crosslink-forming substituent and a light absorbing group in the same molecule as disclosed in U.S. Pat. No. 5,919,599 and the novolak resin type anti-reflective coating having a hydroxyl group being a crosslink-forming substituent and a light absorbing group in the same molecule as disclosed in U.S. Pat. No. 5,693,691, and so on.
The physical properties desired for organic anti-reflective coating include high absorbance to light and radioactive rays, no intermixing with the photoresist layer (being insoluble in photoresist solvents), no diffusion of low molecular substances from the anti-reflective coating material into the topcoat photoresist upon application or baking under heating, and a higher dry etching rate than the photoresist.
On the other hand, the past consideration of technique of anti-reflective coatings has been mainly carried out on lithography process by use of irradiation light having a wavelength of 365 nm, 248 nm or 193 nm. During such consideration, light-absorbing components and light-absorbing groups that efficiently absorb light of each wavelength have been developed, and they have come to be used as one component of the organic anti-reflective coating composition. For example, as to irradiation light of 365 nm, it is known that chalcone dyes resulting from the condensation of 4-hydroxyacetophenone with 4-methoxybenzaldehyde are effective (see, for example patent Document 1), as to irradiation light of 248 nm, it is known that naphthalene group-containing polymers having a specific structure show a high absorbance (see, for example patent Document 2), and as to irradiation light of 193 nm, it is known that resin binder compositions containing phenyl group unit are excellent (see, for example patent Document 3).
In recent years, a lithography process by use of F2 excimer laser beam (wavelength 157 nm) that is a light source having a shorter wavelength comes to be considered as next generation technique for processes by use of ArF excimer laser beam (wavelength 193 nm). The process is supposed to be able to carry out micro-processing of process dimension less than 100 nm, and at present, development and research have been actively done from the side of apparatus, material or the like. However, most of the research on the material relate to photoresists, it is the actual situation that the research on organic anti-reflective coatings is little known. This is because components effectively absorbing light of wavelength 157 nm, that is, light absorbing components having a strong absorption band at 157 nm have been little known.
It is estimated that in lithography process in which F2 excimer laser beam (wavelength 157 nm) is used as irradiation light, process dimension becomes 100 nm or less, therefore from the requirement of aspect ratio, photoresists are thought to be used in a thin film of film thickness of 100 to 300 nm that is thinner than that of the conventional ones. The organic anti-reflective coatings used together with the photoresists in a form of a thin film are required that they can be used in a form of thin film and they have a high selectivity for dry etching compared with photoresists. In addition, in order to use the organic anti-reflective coatings in a form of thin film of 30 to 80 nm, it is considered that the anti-reflective coatings are required to have a high attenuation coefficient (k). In the simulation with PROLITH ver. 5 (manufactured by Litho Tech Japan: as optical constants (refractive index, attenuation coefficient) of photoresist, expected ideal values are used), in case where silicon is used as a base substrate, as the anti-reflective coatings having a film thickness of 30 to 80 nm, coatings having a film thickness of secondary minimum film thickness (about 70 nm) can be used. In this case, the results revealed that the coatings having attenuation coefficient (k) of 0.3 to 0.6 would have a sufficient anti-reflective effect of reflection rate from substrate of 2% or less. As mentioned above, it is thought that a high attenuation coefficient (k), for example 0.3 or more is required in order to obtain a sufficient anti-reflective effect. However, little organic anti-reflective coatings satisfying such attenuation coefficient (k) have been known.
From such circumstances, also in lithography process by use of an irradiation light of wavelength 157 nm, it is desired to develop organic anti-reflective coatings that effectively absorb reflection light from substrates and are excellent in anti-reflective effect.
On the other hand, it is known that anti-reflective coating compositions comprising a fluorine-containing polymer are applied for lithography technique in which F2 excimer laser beam is used as a light source (see, for example patent Document 4). In addition, as anti-reflective coating forming compositions for lithography by use of F2 excimer laser beam, compositions containing halogen atom are known (see, for example patent Document 5).
In addition, in a lithography process by use of ArF excimer laser beam (wavelength 193 nm), in recent years, pattern collapse accompanied with miniaturization of photoresist pattern is becoming a problem. Against this problem, it is designed that aspect ratio is lowed by making a photoresist thinner to prevent pattern collapse. However, as the photoresist acts as a mask in an etching process of semiconductor substrate, it is feared that the photoresist in a form of thinner film causes damage to substrate processing by etching.
Therefore, a process in which a layer composed of an inorganic material called a hard mask is used as an etching stopper is considered in order to solve these problems. For hard masks, materials that absorb light having wavelength 193 nm, such as silicon oxide nitride (SiON) or silicon nitride (SiN) are often used. Thus, it is considered that the anti-reflective coatings used together with the above-mentioned hard mask are required to have a low attenuation coefficient (k) compared with the conventional anti-reflective coatings that are not used together with hard mask. For example, when silicon oxide nitride (SiON) or silicon nitride (SiN) is used as a hard mask and an anti-reflective coating having a film thickness of 20 to 50 nm is used thereon, it is expected that the attenuation coefficient (k) of the anti-reflective coating to a light of wavelength 193 nm is suitably about 0.1 to 0.3 (see, for example Non-patent Document 1). Consequently, it has been desired to develop a new anti-reflective coating.    Patent Document 1: JP-A-11-511194 (1999)    Patent Document 2: JP-A-10-186671 (1998)    Patent Document 3: JP-A-2000-187331 (2000)    Patent Document 4: JP-A-2002-236370 (2002)    Patent Document 5: WO 03/071357 pamphlet    Non-patent Document 1: Proceeding of SPIE, Vol. 5039, 2003, p. 940-947